This invention pertains to ribbon lifting mechanisms for printers such as typewriters.
In order to utilize more fully the available area of printer ribbons which are longitudinally pulled between the print element and the platen there have been devised what has become known as ribbon lifting mechanisms. In general, such a mechanism is raised from a home position below the impact area of the platen or of the print element to such impact area just before the print element strikes the platen. In general, conventional typewriter ribbons are about one-half inch wide and conventional impact areas about one-eighth inch high, thus it is seen that if there is only longitudinal feed of the ribbon a considerable portion of the transverse area of the ribbon is not used. This fact has been long recognized and there are available ribbon feeding mechanisms which ensure that the complete width of ribbon is used. A typical and commonly used ribbon feeding mechanism is described in U.S. Pat. No. 3,171,530, wherein a complicated multiple cam arrangement is used. Such apparatus requires the manufacture of a series of axially arrayed cams which are moved axially with respect to a cam follower in order to achieve the different transverse displacements of the ribbon. It has been found that the presently available mechanism requires one drive for rotating the cams and a second drive for axially displacing the cams with respect to the cam follower. Thus, such devices are not only complex because of the multiple cams and axial displacements but are relatively noisy and subject to considerable wear because of all of the mechanical engagements and disengagements.